1. Field of the Invention
The present invention relates to a process for preparing 5-aminodihydropyrrole which is useful as a raw material of agrochemicals, an oxidepyrrole which is a key intermediate for the preparation of 5-aminodihydropyrrole, and a process for preparing said intermediate.
2. Description of the Related Art
A 5-aminodihydropyrrole of the formula (1): ##STR3## wherein R.sup.1 and R.sup.2 are the same or different and represent a hydrogen atom, a lower alkyl group or a lower haloalkyl group, or together form a C.sub.2 -C.sub.10 alkylene group which may be substituted with a halogen is known to be useful as a raw material of agrochemicals such as benzoxadine or benzoxazoline type herbicides. But, its preparation process has not been known.
As a related process, there is known a process for preparing a 2-substituted-5-aminodihydropyrrole from a corresponding N-oxide compound using sodium and an alcohol, or distilling it in the presence of zinc, or using iron and hydrochloric acid (cf. J. Chem. Soc., (1947) 1508). However, this process is unsatisfactory in the technical production, since sodium, zinc or iron should be used in a large amount and a yield of the desired compound is low.
There is also known a process for preparing 3-phenyl-5-aminodihydropyrrole by treating a 4-phenyl-2-pyrrolidone compound with phosphorus oxychloride and ammonia (cf. Monatsh. Chem., 101 (5), 1970, 1263). However, this process cannot be used for the preparation of a 5-aminodihydropyrrole having no phenyl group at the 3-position such as the 5-aminodihydropyrrole of the formula (1), which is an important raw material of agrochemicals cannot be obtained by this method.
Accordingly, it is highly desired to find a process for preparing the 5-aminodihydropyrrole (1), in particular, which is excellent for industrial scale production.